JP3622163B2 - Tunnel collapse prediction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tunnel collapse prediction method.
[0002]
[Prior art]
Most of the accidents in tunnel construction occur near the face, most of which are based on the collapse near the face.
Measures to prevent the collapse of the face are taken by various means, but the situation of the face must be grasped in case of a collapse.
Therefore, conventionally, a method has been employed in which the displacement of the face is constantly measured and the collapse of the face is predicted from the change in the displacement speed.
It was a method of measuring the state of displacement by embedding an underground displacement meter in the face and electrically extracting data.
[0003]
[Problems to be solved by the present invention]
The conventional tunnel collapse prediction method as described above has the following problems.
<I> Since it is a method of embedding the underground displacement meter itself in the ground, it takes time to install it. Therefore, the displacement cannot be measured immediately after excavation of the face.
<B> Since the displacement meter is expensive, it is difficult to install it at many points. Therefore, the entire displacement is estimated from a small number of measurement points, and an accurate situation cannot be grasped.
<C> Since it is an electric device, it is necessary to wire a signal transmission cord from the face to the measuring device. However, since many excavation-related devices need to work on the face, the presence of the cord tends to hinder the work.
[0004]
The present invention has been made to solve the above-described conventional problems, and can measure changes in the face mountain accurately by a simple installation work and measurement method without substantially obstructing the face work. An object of the present invention is to provide a method for predicting tunnel collapse.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the tunnel collapse prediction method of the present invention includes a steel bar having a tip fixed in the ground of the face, an underground displacement target attached to the exposed end of the steel bar, It is composed of a surface displacement target fixed to the surface and a laser displacement measuring instrument, and features a tunnel collapse prediction method that is performed by measuring the amount of movement of the underground displacement target and the surface displacement target with the laser displacement measuring instrument. Is.
[0006]
[Embodiments of the present invention]
Embodiments of the tunnel collapse prediction method of the present invention will be described below with reference to the drawings.
[0007]
<A> Equipment to be used.
In the prediction method of the present invention, the following equipment is used.
Underground displacement target 1.
Surface displacement target 2.
Laser displacement measuring device 3.
Multi-point collimation device 4.
Control, measurement and alarm device 5.
[0008]
<B> Underground displacement target 1
A small-diameter hole is drilled on the face 6 and a steel rod 7 is inserted and driven into the hole.
As a result, the tip of the steel bar 7 is fixed in the ground of the face 6.
Since the tip is fixed, the steel rod 7 moves according to the behavior of the natural ground, and when the natural ground is pushed out, the steel rod 7 is also pushed out.
A target is attached to the exposed end of the steel bar 7 on the face 6 side, and this is referred to as “underground displacement target 1”.
Since the underground displacement target 1 is fixed to the exposed end of the steel bar 7, it moves with the behavior of the steel bar 7.
When a plurality of steel bars 7 are driven, if the fixed depth of the steel bars 7 is changed, the displacement of the ground at an arbitrary depth can be detected.
[0009]
<C> Surface displacement target 2.
Another target is fixed to the surface of the face 6. The target attached to the surface of the face 6 in this way is referred to as “surface displacement target 2”.
The surface displacement target 2 represents the behavior of the surface as it is, not the behavior inside the face 6.
[0010]
<D> Laser displacement measuring instrument 3.
The laser displacement measuring device 3 is a known device that measures the distance to the target from the difference between the laser transmission time and the reception time.
[0011]
<E> Multipoint collimation device 4.
When multiple targets are installed, the collimation point must be changed sequentially. Therefore, the multipoint collimation device 4 is attached to the laser displacement measuring device 3 as necessary. The positions of all targets to be measured are input in advance to this apparatus. Then, the collimation position of the laser displacement measuring device 3 can be sequentially changed toward each target at regular time intervals.
[0012]
<F> Control, measurement and alarm device 5.
When the multipoint collimation device 4 is attached to the laser displacement measuring instrument 3, the control, measurement and alarm device 5 is further attached. By operating this device, it is possible to calculate the displacement rate, squint, and strain rate at each collimation point.
[0013]
<G> Measuring method.
The laser displacement measuring device 3 collimates the underground displacement target 1 and the surface displacement target 2 at regular intervals and measures the amount of movement.
The amount of displacement in the ground can be known from the amount of movement of the underground displacement target 1, and the amount of displacement of the surface of the face 6 can be known from the amount of movement of the surface displacement target 2.
Therefore, the section displacement in the ground can be calculated by subtracting the displacement of the underground displacement meter from the displacement of the face 6.
Further, the section strain can be calculated by dividing the section displacement by the section length.
[0014]
<H> Collapse prediction method.
By making full use of the above data, the collapse of the face 6 can be predicted by the following method.
(1) If the displacement speed (strain speed) tends to decrease, it can be predicted that the face 6 will be stable.
(2) If the displacement speed (strain speed) tends to increase, it can be predicted that the ground near the face 6 has entered the third creep. From the increasing tendency, the collapse allowance time is calculated, and an alarm is issued if the allowance time is below a certain value. The reference value at this time is set according to the situation at the site.
(3) When the section strain is expected to approach the limit strain of the ground, an alarm is issued.
In this way, the collapse can be predicted in advance to avoid danger.
[0015]
[Effect of the present invention]
Since the tunnel collapse prediction method of the present invention is as described above, the following effects can be obtained.
<B> The steel rod 7 is the only consumable that is required for the collapse prediction.
Since it is inexpensive as described above, it can be installed at a large number of points, and more accurate prediction can be performed than a conventional method in which an expensive device is placed at the decimal point and the displacement is measured.
<B> The preparatory work for the measurement is only placing the steel rod 7. Therefore, since the measurement can be started as soon as excavation of the face 6 is completed, it is possible to always engage in the work of the face 6 with peace of mind.
<C> Unlike conventional electrical measurement methods, there is no need to extend the cord between the face 6 and the measuring device. Therefore, measurement and prediction can be performed without causing any obstacle to the work of the face 6.
<D> By knowing the displacement (strain) speed, an alarm can be automatically issued when the result exceeds a certain value. Therefore, an accident due to the collapse of the face 6 can be prevented in advance.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of a tunnel collapse prediction method according to the present invention. FIG. 2 is an explanatory diagram of a target installation state.

Claims (4)

A steel bar whose tip is fixed in the ground of the face,
An underground displacement target attached to the exposed end of the steel rod;
A surface displacement target fixed to the surface of the face,
Consists of a laser displacement measuring instrument,
By measuring the amount of movement of the underground displacement target and the surface displacement target with a laser displacement measuring instrument,
Tunnel collapse prediction method A steel bar whose tip is fixed in the ground of the face,
An underground displacement target attached to the exposed end of the steel rod;
A surface displacement target fixed to the surface of the face,
Consists of a laser displacement measuring instrument,
Measure the difference between the displacement of the ground displacement target and the surface displacement target with the laser displacement measuring instrument,
By measuring the displacement speed of the face ground,
Tunnel collapse prediction method A steel bar whose tip is fixed in the ground of the face,
An underground displacement target attached to the exposed end of the steel rod;
A surface displacement target fixed to the surface of the face,
A laser displacement measuring instrument,
The multi-point collimation device that sequentially changes the collimation position of the laser displacement measuring instrument toward each target at regular intervals,
By measuring the amount of movement of the underground displacement target and the surface displacement target with a laser displacement measuring instrument,
Tunnel collapse prediction method A steel bar whose tip is fixed in the ground of the face,
An underground displacement target attached to the exposed end of the steel rod;
A surface displacement target fixed to the surface of the face,
A laser displacement measuring instrument,
With alarm device,
Using a laser displacement measuring instrument, measure the amount of movement between the underground displacement target and the surface displacement target,
When the result exceeds a certain value, an alarm is issued by the alarm device.
Tunnel collapse prediction method

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